Transducer with piezoelectric, conductive and dielectric membrane

ABSTRACT

This disclosure provides systems, methods and apparatus for microspeaker devices. In one aspect, a microspeaker element may include a deformable dielectric membrane that spans a speaker cavity. The deformable dielectric membrane can include a piezoactuator and a dielectric layer. Upon application of a driving signal to the piezoactuator, the dielectric layer can deflect, producing sound. In some implementations, an array of microspeaker elements can be encapsulated between a glass substrate and a cover glass. Sound generated by the microspeaker elements can be emitted through a speaker grill formed in the cover glass.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority to U.S.application Ser. No. 14/336,744, filed Jul. 21, 2014 and entitled“TRANSDUCER WITH PIEZOELECTRIC, CONDUCTIVE AND DIELECTRIC MEMBRANE,”which is a continuation of U.S. patent application Ser. No. 13/306,397,filed on Nov. 29, 2011 and entitled “MICROSPEAKER WITH PIEZOELECTRIC,METAL AND DIELECTRIC MEMBRANE,” each of which is incorporated herein bythis reference and for all purposes.

TECHNICAL FIELD

This disclosure relates to electromechanical system devices and moreparticularly to electromechanical microspeaker devices.

DESCRIPTION OF THE RELATED TECHNOLOGY

Electromechanical systems (EMS) include devices having electrical andmechanical elements, actuators, transducers, sensors, optical components(including mirrors) and electronics. Electromechanical systems can bemanufactured at a variety of scales including, but not limited to,microscales and nanoscales. For example, microelectromechanical systems(MEMS) devices can include structures having sizes ranging from about amicron to hundreds of microns or more. Nanoelectromechanical systems(NEMS) devices can include structures having sizes smaller than a micronincluding, for example, sizes smaller than several hundred nanometers.Electromechanical elements may be created using deposition, etching,lithography, and/or other micromachining processes that etch away partsof substrates and/or deposited material layers, or that add layers toform electrical and electromechanical devices.

One type of EMS device is called an interferometric modulator (IMOD).The term interferometric modulator or interferometric light modulatorrefers to a device that selectively absorbs and/or reflects light usingthe principles of optical interference. In some implementations, an IMODmay include a pair of conductive plates, one or both of which may betransparent and/or reflective, wholly or in part, and capable ofrelative motion upon application of an appropriate electrical signal.For example, one plate may include a stationary layer deposited on asubstrate and the other plate may include a reflective membraneseparated from the stationary layer by an air gap. The position of oneplate in relation to another can change the optical interference oflight incident on the IMOD. IMOD devices have a wide range ofapplications, and are anticipated to be used in improving existingproducts and creating new products, especially those with displaycapabilities.

Another type of EMS device is a microspeaker. A microspeaker can convertelectrical signals into sound waves.

SUMMARY

The systems, methods and devices of the disclosure each have severalinnovative aspects, no single one of which is solely responsible for thedesirable attributes disclosed herein.

One innovative aspect of the subject matter described in this disclosurecan be implemented in a microspeaker element. The microspeaker elementmay include a deformable dielectric membrane that spans a speakercavity. The deformable dielectric membrane may include a piezoactuatorand a dielectric layer. Upon application of a driving signal to thepiezoactuator, the dielectric layer can deflect, producing sound. Insome implementations, an array of microspeaker elements may beencapsulated between a glass substrate and a cover glass. Soundgenerated by the microspeaker elements can be emitted through a speakergrill formed in the cover glass.

Another innovative aspect of the subject matter described in thisdisclosure can be implemented in an apparatus including a substrate, adeformable membrane, and a speaker cavity disposed between the substrateand the deformable membrane such that the deformable membrane spans thespeaker cavity. The deformable membrane may include a firstpiezoelectric layer sandwiched between first and second metal layers.The deformable membrane may further include a dielectric layerconfigured to deform on application of a drive voltage across the firstpiezoelectric layer.

In some implementations, the first piezoelectric layer may be disposedbetween the dielectric layer and the substrate. In some implementations,the dielectric layer may be disposed between the first piezoelectriclayer and the substrate. The first piezoelectric layer may have variousconfigurations. For example, the first piezoelectric layer may span thespeaker cavity or overlie only a portion of the speaker cavity accordingto the desired implementation. In some implementations, the firstpiezoelectric layer overlies a peripheral region of the speaker cavity.In some implementations, the first piezoelectric layer is centered overthe speaker cavity.

The deformable membrane may further include a second piezoelectric layersandwiched between third and fourth metal layers. In someimplementations, the first and second piezoelectric layers may belocated on opposite sides of the dielectric layer.

The apparatus may include a display and a processor that is configuredto communicate with the display. The processor may be configured toprocess image data. The apparatus may include a memory device that isconfigured to communicate with the processor. The apparatus may includea driver circuit configured to send at least one signal to the displayand a controller configured to send at least a portion of the image datato the driver circuit. The apparatus may include an image source moduleconfigured to send the image data to the processor. The image sourcemodule may include at least one of a receiver, transceiver, andtransmitter. The apparatus may include an input device configured toreceive input data and to communicate the input data to the processor.

Another innovative aspect of the subject matter described in thisdisclosure can be implemented in an apparatus including an array ofpiezoactuated microspeaker elements. The array may be formed betweenfirst and second joined glass substrates. Each piezoactuatedmicrospeaker element may include a speaker cavity and a deformablemembrane spanning the speaker cavity. The deformable membrane mayinclude a first piezoelectric layer sandwiched between first and secondmetal layers. The deformable membrane may further include a dielectriclayer configured to deform on application of a drive voltage across thepiezoelectric layer. The apparatus may include one or more acousticports formed in a glass substrate and disposed over the array. Theapparatus may include an integrated circuit device positioned in acavity between the first and second glass substrates. The integratedcircuit may be configured to drive the piezoactuated microspeakerelements. The joined glass substrates may be configured to attach to aflexible connector.

Yet another innovative aspect of the subject matter described in thisdisclosure can be implemented in a method of forming a microspeaker. Themethod may include forming a sacrificial layer on a substrate, forming afirst piezoactuator over the sacrificial layer, forming a deformabledielectric layer over the sacrificial layer and the substrate, andremoving the sacrificial layer to form a speaker cavity between thesubstrate and the deformable dielectric layer such that deformabledielectric layer spans the speaker cavity. The method may includeforming a second piezoactuator over the sacrificial layer. In someimplementations, forming the first piezoactuator over the sacrificiallayer may include forming a first metal layer over the sacrificiallayer, forming a first piezoelectric layer over the first metal layer,and forming a second metal layer over the first piezoelectric layer.

Details of one or more implementations of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below. Although the examples provided in this disclosure areprimarily described in terms of electromechanical systems (EMS) andmicroelectromechanical systems (MEMS)-based displays, the conceptsprovided herein may apply to other types of displays, such as liquidcrystal displays, organic light-emitting diode (“OLED”) displays andfield emission displays. Other features, aspects, and advantages willbecome apparent from the description, the figures and the claims. Notethat the relative dimensions of the following figures may not be drawnto scale.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of an isometric view depicting two adjacentpixels in a series of pixels of an interferometric modulator (IMOD)display device.

FIG. 2 shows an example of a system block diagram illustrating anelectronic device incorporating a 3×3 IMOD display.

FIG. 3 shows an example of a diagram illustrating movable reflectivelayer position versus applied voltage for the IMOD of FIG. 1.

FIG. 4 shows an example of a table illustrating various states of anIMOD when various common and segment voltages are applied.

FIG. 5A shows an example of a diagram illustrating a frame of displaydata in the 3×3 IMOD display of FIG. 2.

FIG. 5B shows an example of a timing diagram for common and segmentsignals that may be used to write the frame of display data illustratedin FIG. 5A.

FIG. 6A shows an example of a partial cross-section of the IMOD displayof FIG. 1.

FIGS. 6B-6E show examples of cross-sections of varying implementationsof IMODs.

FIG. 7 shows an example of a flow diagram illustrating a manufacturingprocess for an IMOD.

FIGS. 8A-8E show examples of cross-sectional schematic illustrations ofvarious stages in a method of making an IMOD.

FIGS. 9A-10B show examples of a glass-encapsulated microspeakerincluding a microspeaker array on a glass substrate with a cover glass.

FIG. 11 shows an example of a flow diagram illustrating a manufacturingprocess for a glass-encapsulated microspeaker.

FIGS. 12A-17 show examples of electromechanical microspeaker elementsincluding a deformable dielectric membrane.

FIG. 18 shows an example of a flow diagram illustrating a manufacturingprocess for a microspeaker element.

FIGS. 19A and 19B show examples of system block diagrams illustrating adisplay device that includes a plurality of IMODs.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

The following description is directed to certain implementations for thepurposes of describing the innovative aspects of this disclosure.However, a person having ordinary skill in the art will readilyrecognize that the teachings herein can be applied in a multitude ofdifferent ways. The described implementations may be implemented in anydevice or system that can be configured to display an image, whether inmotion (e.g., video) or stationary (e.g., still image), and whethertextual, graphical or pictorial. More particularly, it is contemplatedthat the described implementations may be included in or associated witha variety of electronic devices such as, but not limited to: mobiletelephones, multimedia Internet enabled cellular telephones, mobiletelevision receivers, wireless devices, smartphones, Bluetooth® devices,personal data assistants (PDAs), wireless electronic mail receivers,hand-held or portable computers, netbooks, notebooks, smartbooks,tablets, printers, copiers, scanners, facsimile devices, GPSreceivers/navigators, cameras, MP3 players, camcorders, game consoles,wrist watches, clocks, calculators, television monitors, flat paneldisplays, electronic reading devices (i.e., e-readers), computermonitors, auto displays (including odometer and speedometer displays,etc.), cockpit controls and/or displays, camera view displays (such asthe display of a rear view camera in a vehicle), electronic photographs,electronic billboards or signs, projectors, architectural structures,microwaves, refrigerators, stereo systems, cassette recorders orplayers, DVD players, CD players, VCRs, radios, portable memory chips,washers, dryers, washer/dryers, parking meters, packaging (such as inelectromechanical systems (EMS), microelectromechanical systems (MEMS)and non-MEMS applications), aesthetic structures (e.g., display ofimages on a piece of jewelry) and a variety of EMS devices. Theteachings herein also can be used in non-display applications such as,but not limited to, electronic switching devices, radio frequencyfilters, sensors, accelerometers, gyroscopes, motion-sensing devices,magnetometers, inertial components for consumer electronics, parts ofconsumer electronics products, varactors, liquid crystal devices,electrophoretic devices, drive schemes, manufacturing processes andelectronic test equipment. Thus, the teachings are not intended to belimited to the implementations depicted solely in the Figures, butinstead have wide applicability as will be readily apparent to onehaving ordinary skill in the art.

Some implementations described herein relate to electromechanicalmicrospeaker elements. In some implementations, a microspeaker elementincludes a speaker cavity disposed between a substrate and a deformabledielectric membrane. The deformable dielectric membrane can include adielectric layer and one or more piezoactuators. Each piezoactuator caninclude at least one piezoelectric layer and electrodes to which a drivesignal can be applied. The drive signal can deflect the piezoelectriclayer, which deflects the dielectric layer thereby producing sound.

Some implementations described herein relate to glass-encapsulatedmicrospeakers. In some implementations, a glass-encapsulatedmicrospeaker includes a glass substrate, an array of electromechanicalmicrospeaker elements disposed on the glass substrate, and a coverglass. The cover glass may be bonded to the glass substrate with anadhesive, such as epoxy, glass frit, or a metal bond ring. The coverglass may include a recess that forms a cavity when the cover glass isbonded to the surface of the glass substrate. The cover glass also mayinclude a speaker grill disposed over the array of microspeaker elementsto allow sound waves to be emitted from the array of microspeakerelements.

Particular implementations of the subject matter described in thisdisclosure can be implemented to realize one or more of the followingpotential advantages. In some implementations, low cost, small size, lowprofile, and low power consumption microspeakers are provided. Further,microspeakers that are fabricated on glass substrates can be compatiblewith displays and other devices that are also fabricated on glasssubstrates, as the microspeakers can either be fabricated jointly withthe other devices or attached as a separate device, the combinationhaving well-matched thermal expansion properties. The materials employedcan result in a high thermal budget that enables reflow or wavesoldering to attach the device to a printed circuit board.

The glass lid and glass substrate of a joined microspeaker can bethermally well matched. One or more acoustic ports in the top, sides, orbottom provide flexibility when mounting the sensor, such as whenmounting in a mobile phone to serve as a speaker or in a speaker array.Through-glass vias in some implementations allow direct connection ofthe microspeaker to a printed circuit or wiring board. In someimplementations, a flexible connector is attachable to the microspeaker,allowing electrical connection to a PCB while allowing the microspeakerto be positioned near an exterior wall or face of an enclosure such as amobile phone case.

An example of a suitable EMS or MEMS device, to which the describedimplementations may apply, is a reflective display device. Reflectivedisplay devices can incorporate interferometric modulators (IMODs) toselectively absorb and/or reflect light incident thereon usingprinciples of optical interference. IMODs can include an absorber, areflector that is movable with respect to the absorber, and an opticalresonant cavity defined between the absorber and the reflector. Thereflector can be moved to two or more different positions, which canchange the size of the optical resonant cavity and thereby affect thereflectance of the IMOD. The reflectance spectrums of IMODs can createfairly broad spectral bands which can be shifted across the visiblewavelengths to generate different colors. The position of the spectralband can be adjusted by changing the thickness of the optical resonantcavity. One way of changing the optical resonant cavity is by changingthe position of the reflector.

FIG. 1 shows an example of an isometric view depicting two adjacentpixels in a series of pixels of an interferometric modulator (IMOD)display device. The IMOD display device includes one or moreinterferometric MEMS display elements. In these devices, the pixels ofthe MEMS display elements can be in either a bright or dark state. Inthe bright (“relaxed,” “open” or “on”) state, the display elementreflects a large portion of incident visible light, e.g., to a user.Conversely, in the dark (“actuated,” “closed” or “off”) state, thedisplay element reflects little incident visible light. In someimplementations, the light reflectance properties of the on and offstates may be reversed. MEMS pixels can be configured to reflectpredominantly at particular wavelengths allowing for a color display inaddition to black and white.

The IMOD display device can include a row/column array of IMODs. EachIMOD can include a pair of reflective layers, i.e., a movable reflectivelayer and a fixed partially reflective layer, positioned at a variableand controllable distance from each other to form an air gap (alsoreferred to as an optical gap or cavity). The movable reflective layermay be moved between at least two positions. In a first position, i.e.,a relaxed position, the movable reflective layer can be positioned at arelatively large distance from the fixed partially reflective layer. Ina second position, i.e., an actuated position, the movable reflectivelayer can be positioned more closely to the partially reflective layer.Incident light that reflects from the two layers can interfereconstructively or destructively depending on the position of the movablereflective layer, producing either an overall reflective ornon-reflective state for each pixel. In some implementations, the IMODmay be in a reflective state when unactuated, reflecting light withinthe visible spectrum, and may be in a dark state when unactuated,reflecting light outside of the visible range (e.g., infrared light). Insome other implementations, however, an IMOD may be in a dark state whenunactuated, and in a reflective state when actuated. In someimplementations, the introduction of an applied voltage can drive thepixels to change states. In some other implementations, an appliedcharge can drive the pixels to change states.

The depicted portion of the pixel array in FIG. 1 includes two adjacentIMODs 12. In the IMOD 12 on the left (as illustrated), a movablereflective layer 14 is illustrated in a relaxed position at apredetermined distance from an optical stack 16, which includes apartially reflective layer. The voltage V₀ applied across the IMOD 12 onthe left is insufficient to cause actuation of the movable reflectivelayer 14. In the IMOD 12 on the right, the movable reflective layer 14is illustrated in an actuated position near or adjacent the opticalstack 16. The voltage V_(bias) applied across the IMOD 12 on the rightis sufficient to maintain the movable reflective layer 14 in theactuated position.

In FIG. 1, the reflective properties of pixels 12 are generallyillustrated with arrows 13 indicating light incident upon the pixels 12,and light 15 reflecting from the pixel 12 on the left. Although notillustrated in detail, it will be understood by one having ordinaryskill in the art that most of the light 13 incident upon the pixels 12will be transmitted through the transparent substrate 20, toward theoptical stack 16. A portion of the light incident upon the optical stack16 will be transmitted through the partially reflective layer of theoptical stack 16, and a portion will be reflected back through thetransparent substrate 20. The portion of light 13 that is transmittedthrough the optical stack 16 will be reflected at the movable reflectivelayer 14, back toward (and through) the transparent substrate 20.Interference (constructive or destructive) between the light reflectedfrom the partially reflective layer of the optical stack 16 and thelight reflected from the movable reflective layer 14 will determine thewavelength(s) of light 15 reflected from the pixel 12.

The optical stack 16 can include a single layer or several layers. Thelayer(s) can include one or more of an electrode layer, a partiallyreflective and partially transmissive layer and a transparent dielectriclayer. In some implementations, the optical stack 16 is electricallyconductive, partially transparent and partially reflective, and may befabricated, for example, by depositing one or more of the above layersonto a transparent substrate 20. The electrode layer can be formed froma variety of materials, such as various metals, for example indium tinoxide (ITO). The partially reflective layer can be formed from a varietyof materials that are partially reflective, such as various metals, suchas chromium (Cr), semiconductors, and dielectrics. The partiallyreflective layer can be formed of one or more layers of materials, andeach of the layers can be formed of a single material or a combinationof materials. In some implementations, the optical stack 16 can includea single semi-transparent thickness of metal or semiconductor whichserves as both an optical absorber and conductor, while different, moreconductive layers or portions (e.g., of the optical stack 16 or of otherstructures of the IMOD) can serve to bus signals between IMOD pixels.The optical stack 16 also can include one or more insulating ordielectric layers covering one or more conductive layers or aconductive/absorptive layer.

In some implementations, the layer(s) of the optical stack 16 can bepatterned into parallel strips, and may form row electrodes in a displaydevice as described further below. As will be understood by one havingskill in the art, the term “patterned” is used herein to refer tomasking as well as etching processes. In some implementations, a highlyconductive and reflective material, such as aluminum (Al), may be usedfor the movable reflective layer 14, and these strips may form columnelectrodes in a display device. The movable reflective layer 14 may beformed as a series of parallel strips of a deposited metal layer orlayers (orthogonal to the row electrodes of the optical stack 16) toform columns deposited on top of posts 18 and an intervening sacrificialmaterial deposited between the posts 18. When the sacrificial materialis etched away, a defined gap 19, or optical cavity, can be formedbetween the movable reflective layer 14 and the optical stack 16. Insome implementations, the spacing between posts 18 may be approximately1-1000 um, while the gap 19 may be approximately less than 10,000Angstroms (Å).

In some implementations, each pixel of the IMOD, whether in the actuatedor relaxed state, is essentially a capacitor formed by the fixed andmoving reflective layers. When no voltage is applied, the movablereflective layer 14 remains in a mechanically relaxed state, asillustrated by the pixel 12 on the left in FIG. 1, with the gap 19between the movable reflective layer 14 and optical stack 16. However,when a potential difference, e.g., voltage, is applied to at least oneof a selected row and column, the capacitor formed at the intersectionof the row and column electrodes at the corresponding pixel becomescharged, and electrostatic forces pull the electrodes together. If theapplied voltage exceeds a threshold, the movable reflective layer 14 candeform and move near or against the optical stack 16. A dielectric layer(not shown) within the optical stack 16 may prevent shorting and controlthe separation distance between the layers 14 and 16, as illustrated bythe actuated pixel 12 on the right in FIG. 1. The behavior is the sameregardless of the polarity of the applied potential difference. Though aseries of pixels in an array may be referred to in some instances as“rows” or “columns,” a person having ordinary skill in the art willreadily understand that referring to one direction as a “row” andanother as a “column” is arbitrary. Restated, in some orientations, therows can be considered columns, and the columns considered to be rows.Furthermore, the display elements may be evenly arranged in orthogonalrows and columns (an “array”), or arranged in non-linear configurations,for example, having certain positional offsets with respect to oneanother (a “mosaic”). The terms “array” and “mosaic” may refer to eitherconfiguration. Thus, although the display is referred to as including an“array” or “mosaic,” the elements themselves need not be arrangedorthogonally to one another, or disposed in an even distribution, in anyinstance, but may include arrangements having asymmetric shapes andunevenly distributed elements.

FIG. 2 shows an example of a system block diagram illustrating anelectronic device incorporating a 3×3 IMOD display. The electronicdevice includes a processor 21 that may be configured to execute one ormore software modules. In addition to executing an operating system, theprocessor 21 may be configured to execute one or more softwareapplications, including a web browser, a telephone application, an emailprogram, or any other software application.

The processor 21 can be configured to communicate with an array driver22. The array driver 22 can include a row driver circuit 24 and a columndriver circuit 26 that provide signals to, e.g., a display array orpanel 30. The cross section of the IMOD display device illustrated inFIG. 1 is shown by the lines 1-1 in FIG. 2. Although FIG. 2 illustratesa 3×3 array of IMODs for the sake of clarity, the display array 30 maycontain a very large number of IMODs, and may have a different number ofIMODs in rows than in columns, and vice versa.

FIG. 3 shows an example of a diagram illustrating movable reflectivelayer position versus applied voltage for the IMOD of FIG. 1. For MEMSIMODs, the row/column (i.e., common/segment) write procedure may takeadvantage of a hysteresis property of these devices as illustrated inFIG. 3. An IMOD may use, for example, about a 10-volt potentialdifference to cause the movable reflective layer, or mirror, to changefrom the relaxed state to the actuated state. When the voltage isreduced from that value, the movable reflective layer maintains itsstate as the voltage drops back below, e.g., 10-volts, however, themovable reflective layer does not relax completely until the voltagedrops below 2-volts. Thus, a range of voltage, approximately 3 to7-volts, as shown in FIG. 3, exists where there is a window of appliedvoltage within which the device is stable in either the relaxed oractuated state. This is referred to herein as the “hysteresis window” or“stability window.” For a display array 30 having the hysteresischaracteristics of FIG. 3, the row/column write procedure can bedesigned to address one or more rows at a time, such that during theaddressing of a given row, pixels in the addressed row that are to beactuated are exposed to a voltage difference of about 10-volts, andpixels that are to be relaxed are exposed to a voltage difference ofnear zero volts. After addressing, the pixels are exposed to a steadystate or bias voltage difference of approximately 5-volts such that theyremain in the previous strobing state. In this example, after beingaddressed, each pixel sees a potential difference within the “stabilitywindow” of about 3-7-volts. This hysteresis property feature enables thepixel design, e.g., illustrated in FIG. 1, to remain stable in either anactuated or relaxed pre-existing state under the same applied voltageconditions. Since each IMOD pixel, whether in the actuated or relaxedstate, is essentially a capacitor formed by the fixed and movingreflective layers, this stable state can be held at a steady voltagewithin the hysteresis window without substantially consuming or losingpower. Moreover, essentially little or no current flows into the IMODpixel if the applied voltage potential remains substantially fixed.

In some implementations, a frame of an image may be created by applyingdata signals in the form of “segment” voltages along the set of columnelectrodes, in accordance with the desired change (if any) to the stateof the pixels in a given row. Each row of the array can be addressed inturn, such that the frame is written one row at a time. To write thedesired data to the pixels in a first row, segment voltagescorresponding to the desired state of the pixels in the first row can beapplied on the column electrodes, and a first row pulse in the form of aspecific “common” voltage or signal can be applied to the first rowelectrode. The set of segment voltages can then be changed to correspondto the desired change (if any) to the state of the pixels in the secondrow, and a second common voltage can be applied to the second rowelectrode. In some implementations, the pixels in the first row areunaffected by the change in the segment voltages applied along thecolumn electrodes, and remain in the state they were set to during thefirst common voltage row pulse. This process may be repeated for theentire series of rows, or alternatively, columns, in a sequentialfashion to produce the image frame. The frames can be refreshed and/orupdated with new image data by continually repeating this process atsome desired number of frames per second.

The combination of segment and common signals applied across each pixel(that is, the potential difference across each pixel) determines theresulting state of each pixel. FIG. 4 shows an example of a tableillustrating various states of an IMOD when various common and segmentvoltages are applied. As will be readily understood by one havingordinary skill in the art, the “segment” voltages can be applied toeither the column electrodes or the row electrodes, and the “common”voltages can be applied to the other of the column electrodes or the rowelectrodes.

As illustrated in FIG. 4 (as well as in the timing diagram shown in FIG.5B), when a release voltage VC_(REL) is applied along a common line, allIMOD elements along the common line will be placed in a relaxed state,alternatively referred to as a released or unactuated state, regardlessof the voltage applied along the segment lines, i.e., high segmentvoltage VS_(H) and low segment voltage VS_(L). In particular, when therelease voltage VC_(REL) is applied along a common line, the potentialvoltage across the modulator (alternatively referred to as a pixelvoltage) is within the relaxation window (see FIG. 3, also referred toas a release window) both when the high segment voltage VS_(H) and thelow segment voltage VS_(L) are applied along the corresponding segmentline for that pixel.

When a hold voltage is applied on a common line, such as a high holdvoltage VC_(HOLD) _(_) _(H) or a low hold voltage VC_(HOLD) _(_) _(L),the state of the IMOD will remain constant. For example, a relaxed IMODwill remain in a relaxed position, and an actuated IMOD will remain inan actuated position. The hold voltages can be selected such that thepixel voltage will remain within a stability window both when the highsegment voltage VS_(H) and the low segment voltage VS_(L) are appliedalong the corresponding segment line. Thus, the segment voltage swing,i.e., the difference between the high VS_(H) and low segment voltageVS_(L), is less than the width of either the positive or the negativestability window.

When an addressing, or actuation, voltage is applied on a common line,such as a high addressing voltage VC_(ADD) _(_) _(H) or a low addressingvoltage VC_(ADD) _(_) _(L), data can be selectively written to themodulators along that line by application of segment voltages along therespective segment lines. The segment voltages may be selected such thatactuation is dependent upon the segment voltage applied. When anaddressing voltage is applied along a common line, application of onesegment voltage will result in a pixel voltage within a stabilitywindow, causing the pixel to remain unactuated. In contrast, applicationof the other segment voltage will result in a pixel voltage beyond thestability window, resulting in actuation of the pixel. The particularsegment voltage which causes actuation can vary depending upon whichaddressing voltage is used. In some implementations, when the highaddressing voltage VC_(ADD) _(_) _(H) is applied along the common line,application of the high segment voltage VS_(H) can cause a modulator toremain in its current position, while application of the low segmentvoltage VS_(L) can cause actuation of the modulator. As a corollary, theeffect of the segment voltages can be the opposite when a low addressingvoltage VC_(ADD) _(_) _(L) is applied, with high segment voltage VS_(H)causing actuation of the modulator, and low segment voltage VS_(L)having no effect (i.e., remaining stable) on the state of the modulator.

In some implementations, hold voltages, address voltages, and segmentvoltages may be used which produce the same polarity potentialdifference across the modulators. In some other implementations, signalscan be used which alternate the polarity of the potential difference ofthe modulators. Alternation of the polarity across the modulators (thatis, alternation of the polarity of write procedures) may reduce orinhibit charge accumulation which could occur after repeated writeoperations of a single polarity.

FIG. 5A shows an example of a diagram illustrating a frame of displaydata in the 3×3 IMOD display of FIG. 2. FIG. 5B shows an example of atiming diagram for common and segment signals that may be used to writethe frame of display data illustrated in FIG. 5A. The signals can beapplied to the, e.g., 3×3 array of FIG. 2, which will ultimately resultin the line time 60 e display arrangement illustrated in FIG. 5A. Theactuated modulators in FIG. 5A are in a dark-state, i.e., where asubstantial portion of the reflected light is outside of the visiblespectrum so as to result in a dark appearance to, e.g., a viewer. Priorto writing the frame illustrated in FIG. 5A, the pixels can be in anystate, but the write procedure illustrated in the timing diagram of FIG.5B presumes that each modulator has been released and resides in anunactuated state before the first line time 60 a.

During the first line time 60 a: a release voltage 70 is applied oncommon line 1; the voltage applied on common line 2 begins at a highhold voltage 72 and moves to a release voltage 70; and a low holdvoltage 76 is applied along common line 3. Thus, the modulators (common1, segment 1), (1,2) and (1,3) along common line 1 remain in a relaxed,or unactuated, state for the duration of the first line time 60 a, themodulators (2,1), (2,2) and (2,3) along common line 2 will move to arelaxed state, and the modulators (3,1), (3,2) and (3,3) along commonline 3 will remain in their previous state. With reference to FIG. 4,the segment voltages applied along segment lines 1, 2 and 3 will have noeffect on the state of the IMODs, as none of common lines 1, 2 or 3 arebeing exposed to voltage levels causing actuation during line time 60 a(i.e., VC_(REL)—relax and VC_(HOLD) _(_) _(L)—stable).

During the second line time 60 b, the voltage on common line 1 moves toa high hold voltage 72, and all modulators along common line 1 remain ina relaxed state regardless of the segment voltage applied because noaddressing, or actuation, voltage was applied on the common line 1. Themodulators along common line 2 remain in a relaxed state due to theapplication of the release voltage 70, and the modulators (3,1), (3,2)and (3,3) along common line 3 will relax when the voltage along commonline 3 moves to a release voltage 70.

During the third line time 60 c, common line 1 is addressed by applyinga high address voltage 74 on common line 1. Because a low segmentvoltage 64 is applied along segment lines 1 and 2 during the applicationof this address voltage, the pixel voltage across modulators (1,1) and(1,2) is greater than the high end of the positive stability window(i.e., the voltage differential exceeded a predefined threshold) of themodulators, and the modulators (1,1) and (1,2) are actuated. Conversely,because a high segment voltage 62 is applied along segment line 3, thepixel voltage across modulator (1,3) is less than that of modulators(1,1) and (1,2), and remains within the positive stability window of themodulator; modulator (1,3) thus remains relaxed. Also during line time60 c, the voltage along common line 2 decreases to a low hold voltage76, and the voltage along common line 3 remains at a release voltage 70,leaving the modulators along common lines 2 and 3 in a relaxed position.

During the fourth line time 60 d, the voltage on common line 1 returnsto a high hold voltage 72, leaving the modulators along common line 1 intheir respective addressed states. The voltage on common line 2 isdecreased to a low address voltage 78. Because a high segment voltage 62is applied along segment line 2, the pixel voltage across modulator(2,2) is below the lower end of the negative stability window of themodulator, causing the modulator (2,2) to actuate. Conversely, because alow segment voltage 64 is applied along segment lines 1 and 3, themodulators (2,1) and (2,3) remain in a relaxed position. The voltage oncommon line 3 increases to a high hold voltage 72, leaving themodulators along common line 3 in a relaxed state.

Finally, during the fifth line time 60 e, the voltage on common line 1remains at high hold voltage 72, and the voltage on common line 2remains at a low hold voltage 76, leaving the modulators along commonlines 1 and 2 in their respective addressed states. The voltage oncommon line 3 increases to a high address voltage 74 to address themodulators along common line 3. As a low segment voltage 64 is appliedon segment lines 2 and 3, the modulators (3,2) and (3,3) actuate, whilethe high segment voltage 62 applied along segment line 1 causesmodulator (3,1) to remain in a relaxed position. Thus, at the end of thefifth line time 60 e, the 3×3 pixel array is in the state shown in FIG.5A, and will remain in that state as long as the hold voltages areapplied along the common lines, regardless of variations in the segmentvoltage which may occur when modulators along other common lines (notshown) are being addressed.

In the timing diagram of FIG. 5B, a given write procedure (i.e., linetimes 60 a-60 e) can include the use of either high hold and addressvoltages, or low hold and address voltages. Once the write procedure hasbeen completed for a given common line (and the common voltage is set tothe hold voltage having the same polarity as the actuation voltage), thepixel voltage remains within a given stability window, and does not passthrough the relaxation window until a release voltage is applied on thatcommon line. Furthermore, as each modulator is released as part of thewrite procedure prior to addressing the modulator, the actuation time ofa modulator, rather than the release time, may determine the necessaryline time. Specifically, in implementations in which the release time ofa modulator is greater than the actuation time, the release voltage maybe applied for longer than a single line time, as depicted in FIG. 5B.In some other implementations, voltages applied along common lines orsegment lines may vary to account for variations in the actuation andrelease voltages of different modulators, such as modulators ofdifferent colors.

The details of the structure of IMODs that operate in accordance withthe principles set forth above may vary widely. For example, FIGS. 6A-6Eshow examples of cross-sections of varying implementations of IMODs,including the movable reflective layer 14 and its supporting structures.FIG. 6A shows an example of a partial cross-section of the IMOD displayof FIG. 1, where a strip of metal material, i.e., the movable reflectivelayer 14 is deposited on supports 18 extending orthogonally from thesubstrate 20. In FIG. 6B, the movable reflective layer 14 of each IMODis generally square or rectangular in shape and attached to supports ator near the corners, on tethers 32. In FIG. 6C, the movable reflectivelayer 14 is generally square or rectangular in shape and suspended froma deformable layer 34, which may include a flexible metal. Thedeformable layer 34 can connect, directly or indirectly, to thesubstrate 20 around the perimeter of the movable reflective layer 14.These connections are herein referred to as support posts. Theimplementation shown in FIG. 6C has additional benefits deriving fromthe decoupling of the optical functions of the movable reflective layer14 from its mechanical functions, which are carried out by thedeformable layer 34. This decoupling allows the structural design andmaterials used for the reflective layer 14 and those used for thedeformable layer 34 to be optimized independently of one another.

FIG. 6D shows another example of an IMOD, where the movable reflectivelayer 14 includes a reflective sub-layer 14 a. The movable reflectivelayer 14 rests on a support structure, such as support posts 18. Thesupport posts 18 provide separation of the movable reflective layer 14from the lower stationary electrode (i.e., part of the optical stack 16in the illustrated IMOD) so that a gap 19 is formed between the movablereflective layer 14 and the optical stack 16, for example when themovable reflective layer 14 is in a relaxed position. The movablereflective layer 14 also can include a conductive layer 14 c, which maybe configured to serve as an electrode, and a support layer 14 b. Inthis example, the conductive layer 14 c is disposed on one side of thesupport layer 14 b, distal from the substrate 20, and the reflectivesub-layer 14 a is disposed on the other side of the support layer 14 b,proximal to the substrate 20. In some implementations, the reflectivesub-layer 14 a can be conductive and can be disposed between the supportlayer 14 b and the optical stack 16. The support layer 14 b can includeone or more layers of a dielectric material, for example, siliconoxynitride (SiON) or silicon dioxide (SiO₂). In some implementations,the support layer 14 b can be a stack of layers, such as, for example, aSiO₂/SiON/SiO₂ tri-layer stack. Either or both of the reflectivesub-layer 14 a and the conductive layer 14 c can include, e.g., analuminum (Al) alloy with about 0.5% copper (Cu), or another reflectivemetallic material. Employing conductive layers 14 a, 14 c above andbelow the dielectric support layer 14 b can balance stresses and provideenhanced conduction. In some implementations, the reflective sub-layer14 a and the conductive layer 14 c can be formed of different materialsfor a variety of design purposes, such as achieving specific stressprofiles within the movable reflective layer 14.

As illustrated in FIG. 6D, some implementations also can include a blackmask structure 23. The black mask structure 23 can be formed inoptically inactive regions (e.g., between pixels or under posts 18) toabsorb ambient or stray light. The black mask structure 23 also canimprove the optical properties of a display device by inhibiting lightfrom being reflected from or transmitted through inactive portions ofthe display, thereby increasing the contrast ratio. Additionally, theblack mask structure 23 can be conductive and be configured to functionas an electrical bussing layer. In some implementations, the rowelectrodes can be connected to the black mask structure 23 to reduce theresistance of the connected row electrode. The black mask structure 23can be formed using a variety of methods, including deposition andpatterning techniques. The black mask structure 23 can include one ormore layers. For example, in some implementations, the black maskstructure 23 includes a molybdenum-chromium (MoCr) layer that serves asan optical absorber, a SiO₂ layer, and an aluminum alloy that serves asa reflector and a bussing layer, with a thickness in the range of about30-80 Å, 500-1000 Å, and 500-6000 Å, respectively. The one or morelayers can be patterned using a variety of techniques, includingphotolithography and dry etching, including, for example, carbontetrafluoride (CF₄) and/or oxygen (O₂) for the MoCr and SiO₂ layers andchlorine (Cl₂) and/or boron trichloride (BCl₃) for the aluminum alloylayer. In some implementations, the black mask 23 can be an etalon orinterferometric stack structure. In such interferometric stack blackmask structures 23, the conductive absorbers can be used to transmit orbus signals between lower, stationary electrodes in the optical stack 16of each row or column. In some implementations, a spacer layer 35 canserve to generally electrically isolate the absorber layer 16 a from theconductive layers in the black mask 23.

FIG. 6E shows another example of an IMOD, where the movable reflectivelayer 14 is self-supporting. In contrast with FIG. 6D, theimplementation of FIG. 6E does not include support posts 18. Instead,the movable reflective layer 14 contacts the underlying optical stack 16at multiple locations, and the curvature of the movable reflective layer14 provides sufficient support that the movable reflective layer 14returns to the unactuated position of FIG. 6E when the voltage acrossthe IMOD is insufficient to cause actuation. The optical stack 16, whichmay contain a plurality of several different layers, is shown here forclarity including an optical absorber 16 a, and a dielectric 16 b. Insome implementations, the optical absorber 16 a may serve both as afixed electrode and as a partially reflective layer.

In implementations such as those shown in FIGS. 6A-6E, the IMODsfunction as direct-view devices, in which images are viewed from thefront side of the transparent substrate 20, i.e., the side opposite tothat upon which the modulator is arranged. In these implementations, theback portions of the device (that is, any portion of the display devicebehind the movable reflective layer 14, including, for example, thedeformable layer 34 illustrated in FIG. 6C) can be configured andoperated upon without impacting or negatively affecting the imagequality of the display device, because the reflective layer 14 opticallyshields those portions of the device. For example, in someimplementations a bus structure (not illustrated) can be included behindthe movable reflective layer 14 which provides the ability to separatethe optical properties of the modulator from the electromechanicalproperties of the modulator, such as voltage addressing and themovements that result from such addressing. Additionally, theimplementations of FIGS. 6A-6E can simplify processing, such aspatterning.

FIG. 7 shows an example of a flow diagram illustrating a manufacturingprocess 80 for an IMOD, and FIGS. 8A-8E show examples of cross-sectionalschematic illustrations of corresponding stages of such a manufacturingprocess 80. In some implementations, the manufacturing process 80 can beimplemented to manufacture, e.g., IMODs of the general type illustratedin FIGS. 1 and 6, in addition to other blocks not shown in FIG. 7. Withreference to FIGS. 1, 6 and 7, the process 80 begins at block 82 withthe formation of the optical stack 16 over the substrate 20. FIG. 8Aillustrates such an optical stack 16 formed over the substrate 20. Thesubstrate 20 may be a transparent substrate such as glass or plastic, itmay be flexible or relatively stiff and unbending, and may have beensubjected to prior preparation processes, e.g., cleaning, to facilitateefficient formation of the optical stack 16. As discussed above, theoptical stack 16 can be electrically conductive, partially transparentand partially reflective and may be fabricated, for example, bydepositing one or more layers having the desired properties onto thetransparent substrate 20. In FIG. 8A, the optical stack 16 includes amultilayer structure having sub-layers 16 a and 16 b, although more orfewer sub-layers may be included in some other implementations. In someimplementations, one of the sub-layers 16 a, 16 b can be configured withboth optically absorptive and conductive properties, such as thecombined conductor/absorber sub-layer 16 a. Additionally, one or more ofthe sub-layers 16 a, 16 b can be patterned into parallel strips, and mayform row electrodes in a display device. Such patterning can beperformed by a masking and etching process or another suitable processknown in the art. In some implementations, one of the sub-layers 16 a,16 b can be an insulating or dielectric layer, such as sub-layer 16 bthat is deposited over one or more metal layers (e.g., one or morereflective and/or conductive layers). In addition, the optical stack 16can be patterned into individual and parallel strips that form the rowsof the display.

The process 80 continues at block 84 with the formation of a sacrificiallayer 25 over the optical stack 16. The sacrificial layer 25 is laterremoved (e.g., at block 90) to form the cavity 19 and thus thesacrificial layer 25 is not shown in the resulting IMODs 12 illustratedin FIG. 1. FIG. 8B illustrates a partially fabricated device including asacrificial layer 25 formed over the optical stack 16. The formation ofthe sacrificial layer 25 over the optical stack 16 may includedeposition of a xenon difluoride (XeF₂)-etchable material such asmolybdenum (Mo) or amorphous silicon (Si), in a thickness selected toprovide, after subsequent removal, a gap or cavity 19 (see also FIGS. 1and 8E) having a desired design size. Deposition of the sacrificialmaterial may be carried out using deposition techniques such as physicalvapor deposition (PVD, e.g., sputtering), plasma-enhanced chemical vapordeposition (PECVD), thermal chemical vapor deposition (thermal CVD), orspin-coating.

The process 80 continues at block 86 with the formation of a supportstructure e.g., a post 18 as illustrated in FIGS. 1, 6 and 8C. Theformation of the post 18 may include patterning the sacrificial layer 25to form a support structure aperture, then depositing a material (e.g.,a polymer or an inorganic material, e.g., silicon oxide) into theaperture to form the post 18, using a deposition method such as PVD,PECVD, thermal CVD, or spin-coating. In some implementations, thesupport structure aperture formed in the sacrificial layer can extendthrough both the sacrificial layer 25 and the optical stack 16 to theunderlying substrate 20, so that the lower end of the post 18 contactsthe substrate 20 as illustrated in FIG. 6A. Alternatively, as depictedin FIG. 8C, the aperture formed in the sacrificial layer 25 can extendthrough the sacrificial layer 25, but not through the optical stack 16.For example, FIG. 8E illustrates the lower ends of the support posts 18in contact with an upper surface of the optical stack 16. The post 18,or other support structures, may be formed by depositing a layer ofsupport structure material over the sacrificial layer 25 and patterningportions of the support structure material located away from aperturesin the sacrificial layer 25. The support structures may be locatedwithin the apertures, as illustrated in FIG. 8C, but also can, at leastpartially, extend over a portion of the sacrificial layer 25. As notedabove, the patterning of the sacrificial layer 25 and/or the supportposts 18 can be performed by a patterning and etching process, but alsomay be performed by alternative etching methods.

The process 80 continues at block 88 with the formation of a movablereflective layer or membrane such as the movable reflective layer 14illustrated in FIGS. 1, 6 and 8D. The movable reflective layer 14 may beformed by employing one or more deposition steps, e.g., reflective layer(e.g., aluminum, aluminum alloy) deposition, along with one or morepatterning, masking, and/or etching steps. The movable reflective layer14 can be electrically conductive, and referred to as an electricallyconductive layer. In some implementations, the movable reflective layer14 may include a plurality of sub-layers 14 a, 14 b, 14 c as shown inFIG. 8D. In some implementations, one or more of the sub-layers, such assub-layers 14 a, 14 c, may include highly reflective sub-layers selectedfor their optical properties, and another sub-layer 14 b may include amechanical sub-layer selected for its mechanical properties. Since thesacrificial layer 25 is still present in the partially fabricated IMODformed at block 88, the movable reflective layer 14 is typically notmovable at this stage. A partially fabricated IMOD that contains asacrificial layer 25 also may be referred to herein as an “unreleased”IMOD. As described above in connection with FIG. 1, the movablereflective layer 14 can be patterned into individual and parallel stripsthat form the columns of the display.

The process 80 continues at block 90 with the formation of a cavity,e.g., cavity 19 as illustrated in FIGS. 1, 6 and 8E. The cavity 19 maybe formed by exposing the sacrificial material 25 (deposited at block84) to an etchant. For example, an etchable sacrificial material such asMo or amorphous Si may be removed by dry chemical etching, e.g., byexposing the sacrificial layer 25 to a gaseous or vaporous etchant, suchas vapors derived from solid XeF₂ for a period of time that is effectiveto remove the desired amount of material, typically selectively removedrelative to the structures surrounding the cavity 19. Other etchingmethods, such as wet etching and/or plasma etching, also may be used.Since the sacrificial layer 25 is removed during block 90, the movablereflective layer 14 is typically movable after this stage. After removalof the sacrificial material 25, the resulting fully or partiallyfabricated IMOD may be referred to herein as a “released” IMOD.

Another example of an EMS device is a microspeaker. In someimplementations, one, two, or multiple microspeakers may be mounted,joined or otherwise connected to one or more EMS devices, such as anIMOD display device. In some implementations, one, two, or multiplemicrospeakers may be fabricated as part of an IMOD display device.

FIGS. 9A and 9B show examples of a glass-encapsulated microspeakerincluding a microspeaker array on a glass substrate with a cover glass.FIG. 9A shows an example of an exploded view diagram of theglass-encapsulated microspeaker. FIG. 9B shows an example of asimplified isometric view of the glass-encapsulated microspeaker shownin FIG. 9A. For clarity, some components shown in FIG. 9A are not shownin FIG. 9B.

The glass-encapsulated microspeaker 100 shown in the example of FIGS. 9Aand 9B includes a cover glass 102, an integrated circuit device 104, aglass substrate 106, a microspeaker array 108, and a joining ring 110.While the cover glass 102 and the glass substrate 106 are depicted astransparent in the FIGS. 9A and 9B, as well as some other Figures, thecover glass and the glass substrate may be transparent ornon-transparent. For example, the cover glass and the glass substratemay be frosted, coated, painted, or otherwise made opaque.

A cover glass can be a planar substrate having two major substantiallyparallel surfaces and one or more recesses. The cover glass 102 includesa recess 112 as shown in FIG. 9A. When the cover glass 102 is bonded tothe glass substrate 106, a cavity 113 is formed as shown in FIG. 9B. Thecavity 113 is a volume that may accommodate different components of theglass-encapsulated microspeaker 100. The cavity 113 in the example ofFIGS. 9A and 9B accommodates the integrated circuit device 104 and themicrospeaker array 108.

In some implementations, the length and the width of the cover glass 102may be the same or approximately the same as the length and the width ofthe glass substrate 106. For example, a length of the cover glass may beabout 1 to 5 mm, and a width of the cover glass may be about 1 to 5 mm.In some implementations, the cover glass and the glass substrate mayhave approximately the same dimensions and may be rectangular or square.In some implementations, the cover glass and the glass substrate mayhave approximately the same dimensions and may be circular, an oval, oranother shape. In various implementations, the cover glass can be about50 to 700 microns thick, for example, about 100 to 300 microns thick,about 300 to 500 microns thick, or about 500 microns thick.

The integrated circuit device 104 can be configured to provide input tothe microspeaker array 108 and can be disposed on the glass substrate106. In some implementations, the integrated circuit device 104 may bean application-specific integrated circuit (ASIC). In the example ofFIGS. 9A and 9B, the integrated circuit device 104 is flip-chip bondedto topside bond pads 127 a on the glass substrate 106. In someimplementations, the integrated circuit device 104 may be wire-bonded tobond pads or fabricated on the surface of the glass substrate 106.

The glass substrate 106 is generally a planar substrate having twosubstantially parallel surfaces, a top surface 126 a and a bottomsurface 126 b. Through-glass vias 122 provide conductive pathwaysbetween portions of the top surface 126 a and the bottom surface 126 bthrough the glass substrate 106. Conductive topside traces 124 on thetop surface 126 a connect the through-glass vias 122 to the topside bondpads 127 a, which provide electrical connections to the integratedcircuit device 104. Bottomside bond pads 127 b on the bottom surface 126b provide bottomside electrical connections to the through-glass vias122. The microspeaker array 108 and the integrated circuit device 104may be electrically connected to one or more of the through-glass vias122 directly or indirectly by the conductive topside traces 124 on theglass substrate 106. In the example shown, conductive topside traces 128connect the microspeaker array 108 to bond pads 129; the bond pads 129may be used for connections to the integrated circuit device 104. Thethrough-glass vias 122 thus provide direct electrical connection fromone or more traces, bond pads, integrated circuit devices, microspeakerelements, and/or other components on one side of the glass substrate 106to one or more traces, bond pads, and/or other components on theopposing side. The particular arrangement of the through-glass vias 122,the conductive topside traces 124, and the topside and bottomside bondpads 127 a and 127 b associated with the glass substrate 106 are anexample of one possible arrangement, with other arrangements possibleaccording to the desired implementation.

In the example shown in FIGS. 9A and 9B, the joining ring 110 surroundsthe through-glass vias 122, the conductive topside traces 124, and thetopside bond pads 127 a. In some implementations, the joining ring 110may overlay some of the conductive topside traces 124 and/or some of thethrough-glass vias 122. Further description of glass substrates andelectrically conductive through-glass vias may be found in U.S. patentapplication Ser. No. 13/048,768, entitled “THIN FILM THROUGH-GLASS VIAAND METHODS FOR FORMING SAME,” filed Mar. 15, 2011, and in U.S. patentapplication Ser. No. 13/221,677, entitled DIE-CUT THROUGH-GLASS VIA ANDMETHODS FOR FORMING SAME,” filed Aug. 30, 2011, which are herebyincorporated by reference.

In some implementations, portions of the conductive topside traces 124on the top surface 126 a that are exposed to the outside environment maybe passivated. For example, the conductive topside traces may bepassivated with a passivation layer, such as a coating of an oxide or anitride. The passivation layer may prevent the conductive topside tracesfrom becoming oxidized and possibly causing failure of theglass-encapsulated microspeaker 100. The passivation layer may bedeposited with a CVD process or PVD process, or other appropriatedeposition technique. Further, other exposed metal surfaces of theglass-encapsulated microspeaker 100 also may be passivated.

In some implementations, a length of the glass substrate 106 may beabout 1 to 5 mm, and a width of the glass substrate 106 may be about 1to 5 mm. In various implementations, the glass substrate 106 can beabout 50 to 700 microns thick, for example, about 100 to 300 micronsthick, about 300 to 500 microns thick, or about 500 microns thick.

The joining ring 110 bonds the cover glass 102 to the glass substrate106. The joining ring 110 may be shaped in any appropriate manner and isgenerally shaped and sized to correspond to the cover glass 102 and theglass substrate 106 to be joined. The joining ring 110 may include anynumber of different bonding materials. In some implementations, thejoining ring 110 may be an adhesive. For example, the joining ring 110may be an epoxy, including an ultraviolet (UV) curable epoxy or aheat-curable epoxy. In some implementations, the joining ring 110 may bea glass frit bond ring. In some implementations, the joining ring 110may be a metal bond ring. The metal bond ring may include a solderablemetallurgy, a eutectic metallurgy, a solder paste, or the like. Examplesof solderable metallurgies include nickel/gold (Ni/Au), nickel/palladium(Ni/Pd), nickel/palladium/gold (Ni/Pd/Au), copper (Cu), and gold (Au).Eutectic metal bonding involves forming a eutectic alloy layer betweenthe cover glass 102 and the glass substrate 106. Examples of eutecticalloys that may be used include indium/bismuth (InBi), copper/tin(CuSn), and gold/tin (AuSn). Melting temperatures of these eutecticalloys are about 150° C. for the InBi eutectic alloy, about 225° C. forthe CuSn eutectic alloy, and about 305° C. for the AuSn eutectic alloy.

The microspeaker array 108 may be formed on or attached to the glasssubstrate 106. The microspeaker array 108 may include any number ofindividual microspeaker elements. For example, the microspeaker array108 can include a 1×1, 1×2, 2×2, 10×10, or 10×20 array of individualmicrospeaker elements. In some implementations, each microspeakerelement includes a deformable dielectric membrane that deflects onreceiving a driving signal, for example, from the integrated circuitdevice 104. Further details of implementations of the microspeakerelements are described below with respect to FIGS. 12A-17. The deformedmembrane generates sound waves that are emitted through a speaker grill115 in the cover glass 102. The speaker grill 115 includes multipleacoustic ports 114 extending through the cover glass 102, through whichsound waves can be transmitted to, e.g., a user. In someimplementations, the deformed membrane can generate sound having afrequency between about 20 Hz and 20,000 Hz, or a portion thereof. Insome implementations, the microspeaker or microspeaker array can besized and driven to generate ultrasonic sound waves up to 40,000 Hz andhigher.

The speaker grill 115 allows sound waves to pass from the microspeakerarray 108 while still allowing the cover glass 102 to protect theinternal components of the glass-encapsulated microspeaker 100. Theacoustic ports 114 in the speaker grill 115 may be in a number ofdifferent configurations, including a single hole or multiple holesarranged in a hexagonal, circular, or square array, for example. Theacoustic ports 114 also may be in any of a number of different shapes,including circular, rectangular, or triangular shapes, for example. Insome implementations, the acoustic ports 114 are designed such that theydo not act as an acoustic cutoff for a sound wave in the frequency rangeto be emitted by the glass-encapsulated microspeaker 100. For example,the diameter of each of the acoustic ports 114 may be large enough andthe depth of each of the acoustic ports 114 may be thin enough to allowmoderately low, medium, and high frequency sound to pass while rollingoff sound waves at low frequencies. Example diameters of the holes rangefrom about 10 to 30 microns on the low side to over 500 microns on thehigh side. In some implementations, the acoustic ports 114 can be coatedwith a hydrophobic material. Examples of hydrophobic coatings includepolytetrafluoroethylene and other fluoropolymers.

FIGS. 10A and 10B show another example of a glass-encapsulatedmicrospeaker including a microspeaker array on a glass substrate with acover glass. FIG. 10A shows an example of an exploded view diagram ofthe glass-encapsulated microspeaker. FIG. 10B shows an example of anisometric view of the glass-encapsulated microspeaker shown in FIG. 10A.

The glass-encapsulated microspeaker 100 shown in FIGS. 10A and 10Bincludes a cover glass 102, an integrated circuit device 104, a glasssubstrate 106, a microspeaker array 108, and a joining ring 110. Thecover glass 102 includes a recess 112 and a speaker grill 115 includingthrough-glass acoustic ports 114. When the cover glass 102 is bonded tothe glass substrate 106, a cavity 113 is formed by the recess 112.

The glass substrate 106 is a substantially planar substrate having twosubstantially parallel surfaces, a top surface 126 a and a bottomsurface 126 b. A ledge 132 allows for electrical connections to portionsof the top surface 126 a enclosed by the cover glass 102. Conductivetopside traces 124 on the top surface 126 a connect topside bond pads127 a to ledge pads 127 c. The topside bond pads 127 a may be used forconnections to the integrated circuit device 104. The microspeaker array108 and the integrated circuit device 104 may be electrically connectedto one or more of the ledge pads 127 c directly or indirectly by theconductive topside traces 124 on the glass substrate 106. In the exampleshown, conductive topside traces 128 connect the microspeaker array 108to bond pads 129, with the bond pads 129 connecting the microspeakerarray 108 to the integrated circuit device 104. The conductive topsidetraces 124 and 128 thus provide electrical connection from one or morebond pads 127 a and 129, integrated circuit device 104, microspeakerarray 108, or other components that may be enclosed by the cover glass102, to one or more ledge pads 127 c or other components. The particulararrangement of the conductive traces, the bond pads, and the ledge padsassociated with the glass substrate 106 are an example of one possiblearrangement, with other arrangements possible according to the desiredimplementation.

In some implementations, portions of the conductive topside traces 124and/or 128 on the top surface 126 a that are exposed to the outsideenvironment may be passivated. For example, the conductive topsidetraces 124 and/or 128 may be passivated with a passivation layer, suchas a coating of an oxide or a nitride.

The joining ring 110 bonds the cover glass 102 to the glass substrate106. The joining ring 110 may include any number of different bondingmaterials, as described above with respect to FIGS. 9A and 9B. In someimplementations, when the joining ring 110 is a metal bond ring bondingthe cover glass 102 to the glass substrate 106, the conductive topsidetraces 124 electrically connecting the topside bond pads 127 a to theledge pads 127 c may be electrically insulated from the metal bond ring.For example, the conductive topside traces 124 may be electricallyinsulated by a passivation layer, as described above.

The glass-encapsulated microspeaker 100 shown in FIGS. 10A and 10B mayfurther include a flexible connector 140, also referred to as a ribboncable, a flexible flat cable, or a flex tape. The flexible connector 140may include a polymer film with embedded electrical connections, such asconducting wires or traces, running parallel to each other on the sameflat plane. The flexible connector 140 also may include flex pads at oneend and contacts at the other end, with the conducting wires or traceselectrically connecting individual flex pads with individual contacts.The flex pads may be on the bottom surface of the flexible connector140, and are not shown in FIG. 10A or 10B. The flex pads may beconfigured to make contact with the ledge pads 127 c. In someimplementations, the flex pads of the flexible connector 140 may bebonded to the ledge pads 127 c of the glass-encapsulated microspeaker100 with an anisotropic conductive film (ACF). In some implementations,the flex pads of the flexible connector 140 may be bonded to the ledgepads 127 c of the glass-encapsulated microspeaker 100 with solder. Thecontacts of the flexible connector 140 may be assembled in a socket orother connector, for example, for connection to a printed circuit board(PCB) or other electronic component.

In some implementations, the glass-encapsulated microspeaker 100 with aledge 132 for connection to a flexible connector 140 may allow theglass-encapsulated microspeaker 100 to be located away from a PCB orother electronic component. When the glass-encapsulated microspeaker 100is located away from a PCB or other electronic component, the PCB may beenclosed within a water resistant enclosure, improving the reliabilityof the electronic device incorporating the glass-encapsulatedmicrospeaker and the PCB. Further, the flexible connector 140 may allowthe glass-encapsulated microspeaker 100 to be mounted near where soundgeneration is desired, such as in in-ear headphones or at the peripheryof a mobile device, such as a cell phone. For example, theglass-encapsulated microspeaker 100 can be located in an in-earheadphone of a user, with some or all of the associated controlelectronics in an IC device located outside the ear. The use of aflexible connector also may obviate a need for electrical vias throughthe glass substrate, which may simplify the fabrication processes forthe glass-encapsulated microspeaker 100.

Various modifications to the examples of glass-encapsulatedmicrospeakers described in reference to FIGS. 9A-10B may be made. Insome implementations, for example, a cover glass of a glass encapsulatedmicrospeaker can include two recesses such that when the cover glass isbonded to the glass substrate, two cavities are formed. In someimplementations, one of these two cavities can accommodate an integratedcircuit device, with the other accommodating a microspeaker array. Insome implementations, a joining ring can separate an integrated circuitdevice from a microspeaker array. In some implementations, aglass-encapsulated microspeaker may not include an integrated circuitdevice disposed between a cover glass and glass substrate. In someimplementations, the microspeaker array can be driven by an externalintegrated circuit device mounted on a flexible connector or PCB, forexample. In some implementations, components such as through-glass vias,conductive traces, and pads may be included on or through a cover glass,instead or in addition to such components on or through a glasssubstrate. In some implementations, the glass-encapsulated microspeakercan include a large side port in the cover glass instead of a speakergrill. Further features of glass packages that may be implemented withthe glass-encapsulated microspeakers described herein are given inco-pending U.S. patent application Ser. Nos. 13/221,701, 13/221,717, andSer. No. 13/221,744, each entitled “GLASS AS A SUBSTRATE MATERIAL AND AFINAL PACKAGE FOR MEMS AND IC DEVICES” and filed Aug. 30, 2011, whichare hereby incorporated by reference.

FIG. 11 shows an example of a flow diagram illustrating a manufacturingprocess for a glass-encapsulated microspeaker. At block 202 of theprocess 200, a glass substrate having an electromechanical microspeakerarray on a surface of the glass substrate is provided. In addition to amicrospeaker array, any number of other components such as joiningrings, conductive traces, pads, vias, ledge pads, and the like may bepresent on any surface of or through the glass substrate. An example ofa manufacturing process for forming microspeaker elements on the surfaceof a glass substrate is discussed below with respect to FIG. 18. Theglass substrate also may have an integrated circuit device disposed onthe surface of the glass substrate. For example, the integrated circuitdevice may be fabricated directly on the surface of the glass substrate,or added as a separate component and attached to the glass substrate. Ifpresent, the integrated circuit device may be configured to drive themicrospeaker array. At block 204, a cover glass including a recess and aspeaker grill is bonded to the surface of the glass substrate. Therecess and speaker grill may be previously formed, for example, with achemical etching process, a reactive ion etching process or asandblasting process. In some implementations, ports of a speaker grillcan be formed by a laser drilling process using, for example, anultraviolet or excimer laser. In some implementations, acoustic portscan be formed after a recess is formed. For example, a recess may beformed in a cover glass by an etching process, with examples of theresulting thickness of the etched portion of the cover glass beingbetween about 200 to 300 microns. Ports extending through the etchedportion of the cover glass can be formed by laser drilling. Examplediameters of laser drilled ports can be between about 10 and 30 microns.As described above, the cover glass may be bonded to the glass substratewith a joining ring that may include any number of different bondingmaterials. In some implementations, the cover glass is bonded to theglass substrate with an adhesive. In some implementations, the coverglass is bonded to the glass substrate with a UV curable epoxy or aheat-curable epoxy. When epoxy is used to bond the cover glass to theglass substrate, the epoxy may be screened or dispensed around the edgesof the cover glass or the glass substrate. Then, the cover glass and theglass substrate may be aligned and pressed together and UV light or heatmay be applied to the epoxy to cure the epoxy.

In some implementations, the cover glass is bonded to the glasssubstrate with a glass frit bond ring. Glass frit may be applied to theglass substrate, cover glass, or both using dispensing, shadow masking,or other appropriate technique. When a glass frit bond ring is used tobond the cover glass to the glass substrate, heat and pressure may beapplied to the cover glass, the glass substrate, and the glass frit bondring when these components are in contact with one another such thatglass frit bond ring melts and bonds the two glass pieces.

In some implementations, the cover glass is bonded to the glasssubstrate with a metal bond ring. When a metal bond ring is used to bondthe cover glass to the glass substrate, heat may be applied to the coverglass, the glass substrate, and the metal bond ring when thesecomponents are in contact with one another such that metal bond ringmelts and bonds the two glass pieces together.

While the process 200 describes an example of a manufacturing processfor a glass-encapsulated microspeaker, a plurality of glass-encapsulatedmicrospeakers may be manufactured with the process 200 with or withoutvariations. For example, tens, hundreds, thousands or more microspeakerarrays may be provided on a single glass substrate panel. Likewise,tens, hundreds, thousands or more recesses and speaker grills can beprovided in a single cover glass panel. The cover glass panel may bebonded to the surface of the glass substrate panel, forming a sheet ofindividually packaged glass-encapsulated microspeakers. Theglass-encapsulated microspeakers may then be separated from one another,for example, by dicing with a diamond blade or a laser, by a scribe andbreak process, or other appropriate technique to cut the joined coverglass and glass substrate panels.

As noted above, a microspeaker array may include any number ofindividual microspeaker elements. The individual microspeaker elementsin the array can be arranged in rows and columns or irregularly suchthat the overall array is in the shape of a polygon, circle, frame,annulus, or another shape. In some implementations, each microspeakerelement includes a deformable dielectric membrane that can deflect uponreceiving a driving voltage signal. FIGS. 12A-17 show examples ofelectromechanical microspeaker elements including a deformabledielectric membrane. FIGS. 12A and 12B show examples of anelectromechanical microspeaker element. FIG. 12A shows an example of atop-down view of the microspeaker element 300. FIG. 12B shows an exampleof a cross-sectional schematic view of the microspeaker element 300through line 1-1 of FIG. 12A. The microspeaker element 300 shown inFIGS. 12A and 12B includes a substrate 305 and a deformable dielectricmembrane 310, which includes a dielectric layer 325 and one or morepiezoactuators 330. The piezoactuator 330 may include a piezoelectricmaterial 350 sandwiched between a first electrode 320 and a secondelectrode 340. A speaker cavity 304 is disposed between the substrate305 and the deformable dielectric membrane 310. In operation, a drivingvoltage can be applied across the first electrode 320 and the secondelectrode 340 to deflect the piezoelectric material 350. The dielectriclayer 325 deflects in turn, producing sound. Conductive traces 335 canconnect the first and second electrodes 320 and 340 to a driver circuit(not shown), which can be located on or off the substrate 305. Inimplementations in which the microspeaker element 300 is one of an arrayof multiple microspeaker elements, the microspeaker element 300 can beconnected in parallel with the other microspeaker elements of the array,for example with the first electrode 320 electrically connected to thelower electrodes and the second electrode 340 electrically connected tothe upper electrodes of piezoactuators of the other microspeakerelements. Furthermore, in implementations in which the microspeakerelement 300 is one of an array of multiple microspeaker elements, eachmicrospeaker element 300 can be driven in phase or with a phase delayand with the same amplitude or different amplitude.

In some implementations, the substrate 305 may be a glass substrate 106as described above in reference to FIGS. 9A-10B. That is, themicrospeaker element 300 may be fabricated on a glass substrate thatforms part of a glass-encapsulated microspeaker as described above. Insome implementations, the microspeaker element 300 may be fabricated ona glass substrate, with that glass substrate incorporated into aglass-encapsulated microspeaker as described above or otherwisepackaged. In some implementations, the substrate 305 can be a non-glasssubstrate such as a plastic, ceramic, silicon, or conductive substrate,with the non-glass substrate incorporated into a glass-encapsulatedmicrospeaker as described above or otherwise packaged. In someimplementations, at least the portion of the substrate 305 that definesthe speaker cavity 304 is substantially planar and can be unetched.Alternatively, a portion of substrate 305 can be etched or otherwiseshaped to form an acoustic cavity underneath the deformable dielectricmembrane 310.

In the example depicted in FIG. 12A, the deformable dielectric membrane310 is circular, however in some other implementations, the deformabledielectric membrane 310 can be any appropriate shape includingrectangular, triangular, square-shaped, or oval-shaped. Examples ofdielectric materials that may be used include silicon oxides, siliconnitrides, silicon oxynitrides, aluminum nitrides, and aluminum oxides.The thickness of the dielectric layer 325 can be between 1 and 10microns, for example. The speaker cavity 304 can be between about 1 and5 microns thick, for example. The distance that the deformabledielectric membrane 310 extends over the speaker cavity 304, alsoreferred to as the span of the deformable dielectric membrane 310, canbe between about 100 and 3000 microns in some implementations. Aperipheral annular region 336 of the deformable dielectric membrane 310can be anchored to the substrate 305. In some implementations, theperipheral annular region 336 is anchored all the way around thedeformable dielectric membrane 310. In some implementations, thedeformable dielectric membrane 310 can be anchored at spaced-apartpositions around its circumference.

The speaker cavity 304 can be sealed or open to ambient conditionsaccording to the desired implementation. In some implementations, thespeaker cavity 304 is sealed to prevent viscous damping. The speakercavity 304 can be at vacuum, sub-atmospheric or atmospheric pressureaccording to the desired implementation. In some implementations, thespeaker cavity 304 is substantially enclosed on all sides such that itis a substantially closed volume. For example, a sealed speaker cavity304 can be defined by the substrate 305 and the deformable dielectricmembrane 310 such that it is enclosed on all sides. In another example,a speaker cavity 304 open to ambient can be defined by the substrate 305and the deformable dielectric membrane 310 such that it is substantiallyenclosed on all sides. One or more vent holes, for example betweendeformable dielectric membrane 310 and the substrate 305, can be presentto allow pressure equilibration of a speaker cavity 304 that issubstantially enclosed on all sides. Vent holes also can be formed inthe deformable dielectric membrane 310 and/or the substrate 305.

The first electrode 320 and the second electrode 340 may include one ormore of a number of different metals, and combinations thereof. Forexample, in various implementations, the first and second electrode 320and 340 may include copper (Cu), nickel (Ni), ruthenium (Ru), tungsten(W), platinum (Pt), molybdenum (Mo), aluminum (Al), titanium (Ti),and/or gold (Au). In some implementations, the first electrode 320 andthe second electrode 340 may be each about 100 to 3000 Angstroms thick.The conductive traces 335 can be formed from the same material as firstelectrode 320 and second electrode 340. The piezoelectric material 350may be any appropriate material such as aluminum nitride (AlN), zincoxide (ZnO) or lead zirconate titanate (PZT). Example thicknesses of thepiezoelectric material may be between about 1 and 3 microns.

In the example of FIG. 12A, the piezoactuator 330 is shown as an annularring at or near a peripheral region of the portion of the deformabledielectric membrane 310 that spans the speaker cavity 304. In someimplementations, the piezoactuator can be any appropriate shapeincluding rectangular, triangular, square-shaped, or oval-shaped rings,for example. In the example of FIG. 12B, a dimension S representing thespan of the deformable dielectric membrane 310 is depicted, as is adimension D1 representing a distance from the edge of the speaker cavity304 to the interior diameter of the piezoactuator 330. In someimplementations, D1 can be equal to about one-sixth of the dimension S,yet, other ratios, both larger and smaller also can be used, forexample. The width of the piezoactuator 330 may or may not be aboutequal to D1 depending on the desired implementation. Example widths ofthe piezoactuator 330 range from a few microns to a few hundred micronsor more. The piezoactuator 330 may contain one or more segments ofpiezoelectric material 350 and associated electrodes 320 and 340.

While the piezoactuator 330 shown in FIG. 12B and other Figures is aunimorph piezoactuator, the piezoactuators of the microspeaker elementsdescribed herein may alternatively be a bimorph piezoactuator. Bimorphpiezoactuators may include two electrode/piezoelectric/electrode stacksseparated by an elastic layer. Examples of elastic layers includesilicon nitrides, silicon oxynitrides, silicon oxides, and aluminumnitrides.

In some implementations, the microspeaker elements described hereinleave a region of the dielectric layer exposed to allow the dielectriclayer to contract and expand in response to a driving signal. Forexample, annular piezoactuators, such as the piezoactuator 330 depictedin FIGS. 12A and 12B, leave a center region of the dielectric layer 325exposed. FIGS. 13A and 13B show examples of an electromechanicalmicrospeaker element that includes a piezoactuator that occupies acenter region of the deformable dielectric membrane. FIG. 13A shows anexample of a top-down view of the microspeaker element 300. FIG. 13Bshows an example of a cross-sectional schematic view of the microspeakerelement 300 through line 1-1 of FIG. 13A. The microspeaker element 300shown in FIGS. 13A and 13B includes a substrate 305, a speaker cavity304, a deformable dielectric membrane 310, and one or more conductivetraces 335, as described above with respect to FIGS. 12A and 12B. Thedeformable dielectric membrane 310 includes a piezoactuator 330 and adielectric layer 325. The piezoactuator 330 occupies a center region ofthe deformable dielectric membrane 310, leaving a peripheral region ofthe dielectric layer 325 uncovered by the piezoactuator 330. Thepiezoactuator 330 includes a piezoelectric material 350 sandwichedbetween a first electrode 320 and a second electrode 340.

In the example depicted in FIG. 13A, the piezoactuator 330 is circular,however in some other implementations, the piezoactuator 330 can be anyappropriate shape including rectangular, triangular, square-shaped, oroval-shaped. In the example of FIG. 13B, a dimension S representing thespan of the deformable dielectric membrane is depicted, as is adimension D2 representing a distance from the edge of the speaker cavity304 to the exterior diameter of the piezoactuator 330. In someimplementations, D2 can be equal to about one-sixth of the dimension S,yet, other ratios, both larger and smaller also can be used, forexample.

FIGS. 14A and 14B show examples of an electromechanical microspeakerelement that includes a “buried” piezoactuator. FIG. 14A shows anexample of a top-down view of the microspeaker element 300. FIG. 14Bshows an example of a cross-sectional schematic view of the microspeakerelement 300 through line 1-1 of FIG. 14A. The microspeaker element 300shown in FIGS. 14A and 14B includes a substrate 305, a speaker cavity304, a deformable dielectric membrane 310, and one or more conductivetraces 335, as described above with respect to FIGS. 12A and 12B. Thedeformable dielectric membrane 310 includes a dielectric layer 325 and acenter-positioned piezoactuator 330. The piezoactuator 330 includes apiezoelectric material 350 sandwiched between a first electrode 320 anda second electrode 340. In the example of FIGS. 14A and 14B, thepiezoactuator 330 is disposed between the speaker cavity 304 and thedielectric layer 325. In some implementations, burying the piezoactuator330 can allow the dielectric layer 325 to protect the piezoactuator 330from humidity and other environmental conditions. A piezoactuator thatis located at or near the periphery of the cavity, such as depicted inFIGS. 12A and 12B, also can be buried.

In some implementations, the microspeaker element can include anacoustic cavity that can improve speaker response to the driving signal,particularly at low frequencies. FIG. 15 shows an example of anelectromechanical microspeaker element connected to an acoustic cavity.The microspeaker element 300 includes a substrate 305, a deformabledielectric membrane 310, and a speaker cavity 304, with the deformabledielectric membrane 310 including a dielectric layer 325 and apiezoactuator 330. The speaker cavity 304 is connected to an acousticcavity 311, which is formed in and extends through the substrate 305.

In some implementations, the microspeaker element can includepiezoactuators on both sides of the dielectric layer. FIGS. 16A-16C showexamples of an electromechanical microspeaker element that includespiezoactuators on both sides of a dielectric layer of the deformabledielectric layer. FIG. 16A shows an example of a top-down view of themicrospeaker element 300. FIGS. 16B and 16C show examples ofcross-sectional schematic views of the microspeaker element 300 throughline 1-1 of FIG. 16A. The microspeaker element 300 shown in FIGS.16A-16C includes a substrate 305, a speaker cavity 304, and a deformabledielectric membrane 310. The deformable dielectric membrane 310 includesa dielectric layer 325, a first piezoactuator 330 a and a secondpiezoactuator 330 b. The first piezoactuator 330 a includes a firstelectrode 320 a, a first piezoelectric layer 350 a, and a secondelectrode 340 a. The second piezoactuator 330 b includes a thirdelectrode 320 b, a second piezoelectric layer 350 b, and a fourthelectrode 340 b. Conductive traces 335 a and 335 b can connect the firstpiezoactuator 330 a and second piezoactuator 330 b, respectively, to adriver circuit (not shown). In some implementations, the firstpiezoactuator 330 a and the second piezoactuator 330 b can be separatelydriven. In some implementations, the first piezoactuator 330 a and thesecond piezoactuator 330 b can be in a push/pull mode, with equal andopposite responses to the driving signal. In some implementations, oneor more electrodes are connected to ground. For example, the innerelectrodes, i.e., the first electrode 320 a and the fourth electrode 340b, can be connected to ground.

The first and second piezoactuators can independently be positioned atthe center or at the periphery of the deformable dielectric membrane. Inthe example of FIG. 16B, the first piezoactuator 330 a and the secondpiezoactuator 330 b both occupy center regions of the deformabledielectric membrane 310. In the example of FIG. 16C, the firstpiezoactuator 330 a is centered, while the second piezoactuator 330 b islocated at or near the periphery of the portion of the deformabledielectric membrane 310 that spans the speaker cavity 304.

In some implementations, the microspeaker can include a piezoactuatorthat spans the cavity of the microspeaker. FIG. 17 shows an example ofan electromechanical microspeaker element 300 including a deformabledielectric membrane 310 on a substrate 305. The deformable dielectricmembrane includes a dielectric layer 325 and a piezoactuator 330. Thepiezoactuator 330 includes a first electrode 320, a piezoelectric layer350, and a second electrode 340. Both the dielectric layer 325 andportions of the piezoactuator 330 span the speaker cavity 304. The firstelectrode 320 and second electrode 340 extend around the periphery ofthe deformable dielectric membrane 310. Alternatively, the firstelectrode 320 and second electrode 340 may be positioned in the centerof the deformable dielectric membrane 310, one on the top and the otheron the bottom of the piezoelectric layer 350. The piezoactuator 330 inFIG. 17 is buried under the dielectric layer 325. In otherimplementations, the piezoactuator can be on top of the dielectric layersuch that the dielectric layer is disposed between the speaker cavityand the piezoactuator.

FIG. 18 shows an example of a flow diagram illustrating a manufacturingprocess for a microspeaker element. Note that the operations of themethod 400 may be combined and/or rearranged to form any of themicrospeaker elements disclosed herein. Note also that the patterningand etching of the different layers, as described below, may beperformed to achieve different patterns of the layers in differentregions of a microspeaker element. Because the operations of the method400 may be performed at about room temperature to 400° C. (i.e., theprocesses of the method may be performed at about 400° C. or lower), themethod 400 is compatible with glass and flat-panel display glasstechnologies.

At block 402, a sacrificial layer is formed on a substrate. As describedabove, the substrate may be a glass substrate that forms aglass-encapsulated microspeaker or a glass or non-glass substrate thatmay be bonded to the glass substrate that forms a glass-encapsulatedmicrospeaker or is otherwise packaged. Prior to forming the sacrificiallayer on the glass substrate, the substrate can be metallized to formthrough-glass vias, conductive traces, bond pads, ledge pads, and thelike. In some implementations, an oxide or a nitride may be deposited topassivate the metal.

The formation of the sacrificial layer may include deposition of asacrificial material by an appropriate deposition technique such assputtering, evaporation, or CVD. Examples of sacrificial materialsinclude gas-etchable materials such as Mo, MoCr, amorphous Si, orpolycrystalline Si. The sacrificial layer is removed in subsequentprocessing to form a speaker cavity, such as speaker cavity 304 in FIG.14B; accordingly, it is deposited to a thickness of the desired size ofthe speaker cavity, which may be about 1 to 5 microns. The formation ofthe sacrificial layer can further include patterning the sacrificialmaterial after deposition to form a desired shape of the cavity. To forma microspeaker element 300 in FIG. 14B, for example, the sacrificialmaterial can be patterned to form a circular shape. In someimplementations, formation of sacrificial layers for an array ofmicrospeaker elements, or for a plurality of arrays of microspeakerelements, can be performed simultaneously by depositing and patterning afilm of sacrificial material across a substrate or portion thereof. Thesacrificial material may be patterned using lithography and etchingprocesses used in integrated circuit manufacturing as known by a personhaving ordinary skill in the art.

At block 404, a piezoactuator is formed over the sacrificial layer. Insome implementations, formation of the piezoactuator can involvedeposition and patterning of a first electrode layer/piezoelectriclayer/second electrode layer stack over the sacrificial layer to formthe piezoactuator in a desired shape. To form a piezoactuator 330 asshown in FIG. 14B, for example, the first electrode/piezoelectriclayer/second electrode stack can be patterned to form a circular shape.One or conductive traces for each of the first and second electrode canbe deposited and patterned during deposition and patterning of theassociated electrode. Patterning, including lithography and etching asknown to a person having ordinary skill in the art, can be performedafter deposition of each layer or only after deposition of the firstelectrode layer/piezoelectric layer/second electrode layer stackaccording to the desired implementation. In some implementations,formation of the first electrode and second electrode layers may includedeposition of a metal such as Cu, Ni, Ru, W, Pt, Mo, Al, Ti, and/or Auby an appropriate deposition process such as sputtering or evaporation.

In some implementations, formation of the piezoelectric layer caninclude deposition of polyvinylidene fluoride (PVDF), aluminum nitride(AlN), lead zirconate titanate (Pb[Zr_(x)Ti_(1-x)]O₃, 0≦x≦1), galliumarsenide (GaAs), zinc oxide (ZnO), or other appropriate material by areactive ion sputtering process, a direct current (DC) sputteringprocess, or other appropriate process. In some implementations,formation of piezoactuators for an array of microspeaker elements, orfor a plurality of arrays of microspeaker elements, can be performedsimultaneously by depositing and patterning a film of sacrificialmaterial across a substrate or portion thereof.

At block 406, a dielectric layer is formed over the sacrificial layer.Examples of dielectric materials include silicon oxides, siliconnitrides, silicon oxynitrides, aluminum nitrides, and aluminum oxides.Formation of the dielectric layer can include deposition of thedielectric material by thermal CVD, PECVD technique, or otherappropriate deposition technique. Formation of the dielectric layer canfurther include patterning the deposited dielectric material. A portionof the dielectric layer may be formed on the glass substrate to providesupport for the portion of the dielectric layer formed over thesacrificial layer. As with the sacrificial layer and piezoactuator,formation of dielectric layers for an array of microspeaker elements, orfor a plurality of arrays of microspeaker elements, can be performedsimultaneously.

According to various implementations, block 404 can be performed priorto or after block 406. For example, to form a microspeaker element 300as depicted in the example of FIG. 12B, block 404 may be performed afterblock 406, such that the piezoactuator is formed on the dielectriclayer. In some implementations, block 404 may be performed prior to andafter block 406.

At block 408, the sacrificial layer is removed. In some implementations,removing the sacrificial layer involves exposing it to an etchant. Forexample, a gas-etchable material such as Mo or amorphous Si may beremoved by dry chemical etching with vapors derived from solid XeF2 orother fluorine-based etchant. Other combinations of etchable sacrificialmaterial and etching methods, such as wet etching and/or plasma etching,also may be used.

As indicated above, various modifications can be made to the method 400to form any of the microspeaker elements described herein. Inimplementations of microspeaker elements including non-piezoelectricelastic layers, an elastic layer including silicon nitride (SiN),silicon oxynitride (SiON), silicon oxide (SiO₂), silicon (Si), aluminumnitride (AlN), a metal, or a polymer, for example, may be formed usingan appropriate processing technique, as know by a person having ordinaryskill in the art. For example, an elastic layer may be formed with asputtering process, a chemical vapor deposition (CVD) process, aphysical vapor deposition (PVD) process, or an electroplating process.

As indicated above, in some implementations, a glass package asdescribed herein can be part of a display device. In some otherimplementations, non-display devices fabricated on glass substrates canbe compatible with displays and other devices that are also fabricatedon glass substrates, with the non-display devices fabricated jointlywith a display device or attached as a separate device, the combinationhaving well-matched thermal expansion properties.

FIGS. 19A and 19B show examples of system block diagrams illustrating adisplay device 40 that includes a plurality of IMODs. The display device40 can be, for example, a smart phone, a cellular or mobile telephone.However, the same components of the display device 40 or slightvariations thereof are also illustrative of various types of displaydevices such as televisions, tablets, e-readers, hand-held devices andportable media players.

The display device 40 includes a housing 41, a display 30, an antenna43, a speaker 45, an input device 48 and a microphone 46. The housing 41can be formed from any of a variety of manufacturing processes,including injection molding, and vacuum forming. In addition, thehousing 41 may be made from any of a variety of materials, including,but not limited to: plastic, metal, glass, rubber and ceramic, or acombination thereof. The housing 41 can include removable portions (notshown) that may be interchanged with other removable portions ofdifferent color, or containing different logos, pictures, or symbols.

The display 30 may be any of a variety of displays, including abi-stable or analog display, as described herein. The display 30 alsocan be configured to include a flat-panel display, such as plasma, EL,OLED, STN LCD, or TFT LCD, or a non-flat-panel display, such as a CRT orother tube device. In addition, the display 30 can include an IMODdisplay, as described herein.

The components of the display device 40 are schematically illustrated inFIG. 19B. The display device 40 includes a housing 41 and can includeadditional components at least partially enclosed therein. For example,the display device 40 includes a network interface 27 that includes anantenna 43 which is coupled to a transceiver 47. The transceiver 47 isconnected to a processor 21, which is connected to conditioning hardware52. The conditioning hardware 52 may be configured to condition a signal(e.g., filter a signal). The conditioning hardware 52 is connected to aspeaker 45 and a microphone 46. The processor 21 is also connected to aninput device 48 and a driver controller 29. The driver controller 29 iscoupled to a frame buffer 28, and to an array driver 22, which in turnis coupled to a display array 30. In some implementations, a powersupply 50 can provide power to substantially all components in theparticular display device 40 design.

The network interface 27 includes the antenna 43 and the transceiver 47so that the display device 40 can communicate with one or more devicesover a network. The network interface 27 also may have some processingcapabilities to relieve, for example, data processing requirements ofthe processor 21. The antenna 43 can transmit and receive signals. Insome implementations, the antenna 43 transmits and receives RF signalsaccording to the IEEE 16.11 standard, including IEEE 16.11(a), (b), or(g), or the IEEE 802.11 standard, including IEEE 802.11a, b, g, n, andfurther implementations thereof. In some other implementations, theantenna 43 transmits and receives RF signals according to the BLUETOOTHstandard. In the case of a cellular telephone, the antenna 43 isdesigned to receive code division multiple access (CDMA), frequencydivision multiple access (FDMA), time division multiple access (TDMA),Global System for Mobile communications (GSM), GSM/General Packet RadioService (GPRS), Enhanced Data GSM Environment (EDGE), TerrestrialTrunked Radio (TETRA), Wideband-CDMA (W-CDMA), Evolution Data Optimized(EV-DO), 1×EV-DO, EV-DO Rev A, EV-DO Rev B, High Speed Packet Access(HSPA), High Speed Downlink Packet Access (HSDPA), High Speed UplinkPacket Access (HSUPA), Evolved High Speed Packet Access (HSPA+), LongTerm Evolution (LTE), AMPS, or other known signals that are used tocommunicate within a wireless network, such as a system utilizing 3G or4G technology. The transceiver 47 can pre-process the signals receivedfrom the antenna 43 so that they may be received by and furthermanipulated by the processor 21. The transceiver 47 also can processsignals received from the processor 21 so that they may be transmittedfrom the display device 40 via the antenna 43.

In some implementations, the transceiver 47 can be replaced by areceiver. In addition, in some implementations, the network interface 27can be replaced by an image source, which can store or generate imagedata to be sent to the processor 21. The processor 21 can control theoverall operation of the display device 40. The processor 21 receivesdata, such as compressed image data from the network interface 27 or animage source, and processes the data into raw image data or into aformat that is readily processed into raw image data. The processor 21can send the processed data to the driver controller 29 or to the framebuffer 28 for storage. Raw data typically refers to the information thatidentifies the image characteristics at each location within an image.For example, such image characteristics can include color, saturationand gray-scale level.

The processor 21 can include a microcontroller, CPU, or logic unit tocontrol operation of the display device 40. The conditioning hardware 52may include amplifiers and filters for transmitting signals to thespeaker 45, and for receiving signals from the microphone 46. Theconditioning hardware 52 may be discrete components within the displaydevice 40, or may be incorporated within the processor 21 or othercomponents.

The driver controller 29 can take the raw image data generated by theprocessor 21 either directly from the processor 21 or from the framebuffer 28 and can re-format the raw image data appropriately for highspeed transmission to the array driver 22. In some implementations, thedriver controller 29 can re-format the raw image data into a data flowhaving a raster-like format, such that it has a time order suitable forscanning across the display array 30. Then the driver controller 29sends the formatted information to the array driver 22. Although adriver controller 29, such as an LCD controller, is often associatedwith the system processor 21 as a stand-alone Integrated Circuit (IC),such controllers may be implemented in many ways. For example,controllers may be embedded in the processor 21 as hardware, embedded inthe processor 21 as software, or fully integrated in hardware with thearray driver 22.

The array driver 22 can receive the formatted information from thedriver controller 29 and can re-format the video data into a parallelset of waveforms that are applied many times per second to the hundreds,and sometimes thousands (or more), of leads coming from the display'sx-y matrix of pixels.

In some implementations, the driver controller 29, the array driver 22,and the display array 30 are appropriate for any of the types ofdisplays described herein. For example, the driver controller 29 can bea conventional display controller or a bi-stable display controller(such as an IMOD controller). Additionally, the array driver 22 can be aconventional driver or a bi-stable display driver (such as an IMODdisplay driver). Moreover, the display array 30 can be a conventionaldisplay array or a bi-stable display array (such as a display includingan array of IMODs). In some implementations, the driver controller 29can be integrated with the array driver 22. Such an implementation canbe useful in highly integrated systems, for example, mobile phones,portable-electronic devices, watches or small-area displays.

In some implementations, the input device 48 can be configured to allow,for example, a user to control the operation of the display device 40.The input device 48 can include a keypad, such as a QWERTY keyboard or atelephone keypad, a button, a switch, a rocker, a touch-sensitivescreen, a touch-sensitive screen integrated with display array 30, or apressure- or heat-sensitive membrane. The microphone 46 can beconfigured as an input device for the display device 40. In someimplementations, voice commands through the microphone 46 can be usedfor controlling operations of the display device 40.

The power supply 50 can include a variety of energy storage devices. Forexample, the power supply 50 can be a rechargeable battery, such as anickel-cadmium battery or a lithium-ion battery. In implementationsusing a rechargeable battery, the rechargeable battery may be chargeableusing power coming from, for example, a wall socket or a photovoltaicdevice or array. Alternatively, the rechargeable battery can bewirelessly chargeable. The power supply 50 also can be a renewableenergy source, a capacitor, or a solar cell, including a plastic solarcell or solar-cell paint. The power supply 50 also can be configured toreceive power from a wall outlet.

In some implementations, control programmability resides in the drivercontroller 29 which can be located in several places in the electronicdisplay system. In some other implementations, control programmabilityresides in the array driver 22. The above-described optimization may beimplemented in any number of hardware and/or software components and invarious configurations.

The various illustrative logics, logical blocks, modules, circuits andalgorithm steps described in connection with the implementationsdisclosed herein may be implemented as electronic hardware, computersoftware, or combinations of both. The interchangeability of hardwareand software has been described generally, in terms of functionality,and illustrated in the various illustrative components, blocks, modules,circuits and steps described above. Whether such functionality isimplemented in hardware or software depends upon the particularapplication and design constraints imposed on the overall system.

The hardware and data processing apparatus used to implement the variousillustrative logics, logical blocks, modules and circuits described inconnection with the aspects disclosed herein may be implemented orperformed with a general purpose single- or multi-chip processor, adigital signal processor (DSP), an application specific integratedcircuit (ASIC), a field programmable gate array (FPGA) or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described herein. A general purpose processor may be amicroprocessor, or, any conventional processor, controller,microcontroller, or state machine. A processor also may be implementedas a combination of computing devices, such as a combination of a DSPand a microprocessor, a plurality of microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration. In some implementations, particular steps and methods maybe performed by circuitry that is specific to a given function.

In one or more aspects, the functions described may be implemented inhardware, digital electronic circuitry, computer software, firmware,including the structures disclosed in this specification and theirstructural equivalents thereof, or in any combination thereof.Implementations of the subject matter described in this specificationalso can be implemented as one or more computer programs, i.e., one ormore modules of computer program instructions, encoded on a computerstorage media for execution by, or to control the operation of, dataprocessing apparatus.

If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. The steps of a method or algorithm disclosedherein may be implemented in a processor-executable software modulewhich may reside on a computer-readable medium. Computer-readable mediaincludes both computer storage media and communication media includingany medium that can be enabled to transfer a computer program from oneplace to another. A storage media may be any available media that may beaccessed by a computer. By way of example, and not limitation, suchcomputer-readable media may include RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that may be used to store desired programcode in the form of instructions or data structures and that may beaccessed by a computer. Also, any connection can be properly termed acomputer-readable medium. Disk and disc, as used herein, includescompact disc (CD), laser disc, optical disc, digital versatile disc(DVD), floppy disk, and blu-ray disc where disks usually reproduce datamagnetically, while discs reproduce data optically with lasers.Combinations of the above also may be included within the scope ofcomputer-readable media. Additionally, the operations of a method oralgorithm may reside as one or any combination or set of codes andinstructions on a machine readable medium and computer-readable medium,which may be incorporated into a computer program product.

Various modifications to the implementations described in thisdisclosure may be readily apparent to those skilled in the art, and thegeneric principles defined herein may be applied to otherimplementations without departing from the spirit or scope of thisdisclosure. Thus, the claims are not intended to be limited to theimplementations shown herein, but are to be accorded the widest scopeconsistent with this disclosure, the principles and the novel featuresdisclosed herein. The word “exemplary” is used exclusively herein tomean “serving as an example, instance, or illustration.” Anyimplementation described herein as “exemplary” is not necessarily to beconstrued as preferred or advantageous over other possibilities orimplementations. Additionally, a person having ordinary skill in the artwill readily appreciate, the terms “upper” and “lower” are sometimesused for ease of describing the figures, and indicate relative positionscorresponding to the orientation of the figure on a properly orientedpage, and may not reflect the proper orientation of an IMOD asimplemented.

Certain features that are described in this specification in the contextof separate implementations also can be implemented in combination in asingle implementation. Conversely, various features that are describedin the context of a single implementation also can be implemented inmultiple implementations separately or in any suitable subcombination.Moreover, although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, a person having ordinary skill in the art will readily recognizethat such operations need not be performed in the particular order shownor in sequential order, or that all illustrated operations be performed,to achieve desirable results. Further, the drawings may schematicallydepict one more example processes in the form of a flow diagram.However, other operations that are not depicted can be incorporated inthe example processes that are schematically illustrated. For example,one or more additional operations can be performed before, after,simultaneously, or between any of the illustrated operations. In certaincircumstances, multitasking and parallel processing may be advantageous.Moreover, the separation of various system components in theimplementations described above should not be understood as requiringsuch separation in all implementations, and it should be understood thatthe described program components and systems can generally be integratedtogether in a single software product or packaged into multiple softwareproducts. Additionally, other implementations are within the scope ofthe following claims. In some cases, the actions recited in the claimscan be performed in a different order and still achieve desirableresults.

What is claimed is:
 1. An apparatus comprising: an array of elements,each element including a cavity and a deformable membrane spanning thecavity, the deformable membrane including a first piezoelectric layerbetween first and second metal layers and including a dielectric layer,wherein the dielectric layer is capable of deforming on application of adrive voltage across the piezoelectric layer to generate an ultrasonicwave.
 2. The apparatus of claim 1, wherein the array of elements isbetween a first substrate and a second substrate, wherein the firstsubstrate is joined to the second substrate.
 3. The apparatus of claim2, wherein the second glass substrate includes one or more acousticports such that the acoustic ports are disposed over the array.
 4. Theapparatus of claim 2, further comprising an integrated circuit devicepositioned in a second cavity between the first glass substrate and thesecond glass substrate, the integrated circuit being configured to drivethe elements.
 5. The apparatus of claim 1, wherein the elements of thearray are configured to connect to an external integrated circuitdevice.
 6. The apparatus of claim 1, further comprising a firstsubstrate, wherein each element in the array is formed on the firstsubstrate.
 7. The apparatus of claim 1, wherein the elements in thearray are configured in at least one row and at least one column.
 8. Theapparatus of claim 1, wherein the elements in the array are electricallyconnected in parallel.
 9. The apparatus of claim 1, wherein the elementsin the array are driven in phase with the same amplitude upon theapplication of the drive voltage.
 10. The apparatus of claim 1, whereinthe elements in the array are driven in phase with a different amplitudeupon the application of the drive voltage.
 11. A display deviceincluding the apparatus of claim 1, wherein the elements in the arrayare encapsulated between a first substrate and a cover glass of thedisplay.
 12. The display device of claim 11, wherein the first substrateis bonded to the cover glass with one of an adhesive, an epoxy, a glassfrit, or a metal bond ring.
 13. The display device of claim 11,including one of a bi-stable display, an analog display, a flat-paneldisplay, a plasma display, an electroluminescent display, an organiclight-emitting diode (OLED) display, a liquid crystal (LCD) display, anon-flat-panel display, a reflective display, and an IMOD display. 14.The display device of claim 11, wherein the cover glass of the displayincludes a plurality of acoustic ports extending through the cover glassto allow transmission of the ultrasonic wave.
 15. The display device ofclaim 14, wherein a diameter of the acoustic ports is between 10 micronsand 500 microns.
 16. The display device of claim 14, wherein theacoustic ports are coated with a hydrophobic material.
 17. The displaydevice of claim 11, wherein the cover glass has a thickness between 50microns and 700 microns.
 18. A method, comprising: forming a firstpiezoactuator over a substrate; forming a deformable dielectric layerover the substrate; and forming a cavity between the substrate and thedeformable dielectric layer such that deformable dielectric layer spansthe cavity.
 19. The method of claim 18, wherein forming the firstpiezoactuator over the substrate includes forming a first metal layerover the substrate, forming a first piezoelectric layer over the firstmetal layer, and forming a second metal layer over the firstpiezoelectric layer.
 20. The method of claim 19, further comprisingforming a second piezoactuator over the deformable dielectric layer.